Skip to content
Home » An inconvenient truth revisited

An inconvenient truth revisited

  • marimac 

By Jan Lievens

In my last article I obviously touched a rather damaged nerve that over the years is probably shot by now.

But be that as it may, there are some good expressions that cover it. In Dutch they call it somebody is ‘een luis in die pels’. Freely translated, I must be the thorn on the side or even in the flesh for certain lobby groups.

Let me explain in the context of our applied postharvest technology field. In theory, ‘normal’ cold stores do have unpleasant side effects from a high humidity in the atmosphere. When cold room doors are opened, a turbulent exchange of air occurs across the door space. Moisture from the outside air condenses on the cold store floor and other surfaces, producing ice, frost and even snow.

Applied postharvest technology implementation will be critical for the South African producers to compete with the demands of global quality in the future. Image credit: Creative Commons | Unsplash

Applied postharvest technology implementation will be critical for the South African producers to compete with the demands of global quality in the future. Image credit: Creative Commons | Unsplash

Moisture entering a cold room will also freeze on evaporator coils. Frosted coils are inefficient, and defrosting can be expensive. That is exactly what the average refrigeration engineer will tell you. But outside air intrusion can be kept to a minimum with simple measurements, and it is true when you are busy cooling a lot of commodities, except fruit, vegetables, and flowers which are living objects.

Here, special considerations should be applied in the design: bigger coils, wider fins and controllable windspeeds to name just a few. And there are many more. You are working with living structures with lots of water inside of them.

Cold room designs and procedures should start recognising that high wind speeds with too low RH cause damage. Fast-cooling walls that are now implemented in the table grape and berry industries, where huge wind speeds are chased over open product, are simply the new walls of death.

Register for free to gain access the digital library for Cold Link Africa publications

If I were Dr Dolittle and I could talk to the fruit instead of the animals, I would hear the most excruciating sounds coming from a torture practice that would have both global intelligence agencies and rogue units blushing.

For those of you who do work with me, you will find out that the emphasis in postharvest cooling lies on the thorough pre-cooling, where the temperatures in general don’t go too low as you pre-cool to the temperatures the packing facility is working at. But in saying that, there is a whole philosophy that comes with it. Always.

Of course, defrost is an ever-occurring phenomena, but at least with proper RH technology, the water comes from the system and not from the fruit, vegetable, and/or flowers.

And when I say, “proper technology”, I mean it. Hot air can handle and hold more moisture volume than cold air, hence the fact that RH must be controlled with a proper system to adjust the amount of RH you always put in a room as the air temperature and the capacity of holding water continuously changes. Otherwise, just as in your fridge at home, whatever is in there unprotected, dries out, it is a natural process.

Aside from that, in the specific cooling process, you know at least that the defrost is coming from the RH machines and not from your fruit. Another example is the saying “that our cold room designs are designed for 95% RH”. Fair enough and you know what, when you measure the RH after a prolonged period of cooling like in a controlled atmosphere (CA) store, the RH is indeed 95% after a good couple of months.

The question is whether you ever measured your RH levels at the beginning? Nope, nine out of ten do not do it and any professional CA operator will tell you, that the defrost in a CA room is during the first two to three weeks after they start up the room.

Now, when you open that CA room, you will see that the fruit level of ALL the bins simply is lowered by 12-15 cm compared to the picking height. Do the engineers install hydraulic vibrating floors which makes the fruit sit snug close to each other? I don’t think so…

Register for free to gain access the digital library for Cold Link Africa publications

But it makes you think. Your fruit loses quality, never mind weight. In field tests, a similar comparable room packed out 17% more fruit with the correct RH technology. It is just not about selling machines at all, it is a method on how to handle live material, that in fact do consists of a whole lot of water.

Anybody “just selling machines” without thorough knowledge of the process that takes place once you cut the umbilical cord of the fruit should be chased off the facility in any case.

I was sitting in a Zoom seminar the other day which was brilliantly organised and well presented. All fruits were handled, and it was just fun sitting in and being quiet.

Until a point was reached where I frowned my eyebrows in such a way I nearly fainted!

In the stone fruit session, the use of ‘wet blankets’ on top of harvesting crates was discussed to cool down initial field heat. Really? And then they complain about shrivel.

If you look this method up on Google, you will find a research report on how to cool fruit in Rwanda and Burkina Faso, there they use wet blankets. Ladies, and Gents, we are on another level, delivering to other markets that more and more demand high quality without having to throw produce away.

If South Africa wants to keep competing in an ever more-demanding international market, it will be by supplying superior top quality, and applied postharvest technology implementation will have to be a part of that process. Pinching nerves or not?

But didn’t Cees Nijssen talk about that in his interview with The Cold Link in 1999?

Unlike cooling of other products or processes, fruit, vegetables, and flowers are living objects. Image supplied

Unlike cooling of other products or processes, fruit, vegetables, and flowers are living objects. Image supplied

Again, that is now 22 years ago. It also reminded me of a farm in Tulbagh that sorted out the shrivel with his plums a couple of years ago. He simply ripped out the orchard. That is one way of solving it. But it also shows that if the industry is misinformed, sometimes very costly mistakes are made. These should be avoided at all costs.

Then, in the Table Grape session of the seminar, the effect of condensation in the grape packaging and the subsequent SO₂ damage on the grapes reached the panel. I do have news for you, when a proper temperature management regime would be followed with the correct airflow design in the cartons and an adapted inner packaging that gives the cooling machines to do a proper job, condensation shouldn’t be a problem at all.

I have been saying it for years: “95% of the farm’s efforts that they are doing are absolutely perfect, the last 5%, giving the farm 99% of their income, is neglected”. In general, our farmers are the best in the world, but when they deliver better quality to their clients, both the farm and clients and will be better off.

A strong suggestion is to go and look at the theory of root cause analysis. Start tackling the problems at roots level instead of treating symptoms of an initial problem. When I see thermal image pictures of cooled pallets, where on the one side they measure 0.8° C and release the product for export, and the other side shows 14.8° C, I really get the creeps.

When you then get reports from the shipping container, you will see that the temperatures are not kept, and the container balances out the differences. This results in the colder fruit side warming up and the hotter side cooling down. Both natural processes that create condensation. Cold fruit in hot temperatures or hot fruit in cold temperatures, simply create condensation and do create havoc with huge quality consequences.

Get to the roots of the problem and stop chasing symptoms, just now some of you must apply for a Don Quichotte license. And start implementing correct postharvest procedures without fooling yourself.

Do you want to know what the real problem is? We often still see designs that saw their birth nearly 40 years ago. Change is inevitable and applies in this industry. Adapt or die is a famous saying, but the problem is that the designers often do not feel the effect of their designs, the farm does.

Inconvenient truth? Maybe, but you will have to face it at some stage before it bites you in the back or worse in another place that is not really suited for publication.

Till the next time and hopefully you find a way to listen to the sound of your tortured fruit as well. I am sure it comes over like the sound of breaking glass from Nick Lowe…

About Jan Lievens

Jan Lievens, born in Belgium, is a graduate civil engineering(B) and international senior consultant for engineered applied postharvest technology at UTE South Africa. With over 20 years of experience in this field, he is widely regarded as a specialist in the fruit-, vegetable- and flower industry with regards to humidity, airborne bacteria and ethylene removal, both locally and internationally. Furthermore, he also designed airflow-friendly packaging systems for the industry with proven results.

Jan Lievens, born in Belgium, is a graduate civil engineering(B) and international senior consultant for engineered applied postharvest technology at UTE South Africa. With over 20 years of experience in this field, he is widely regarded as a specialist in the fruit-, vegetable- and flower industry with regards to humidity, airborne bacteria and ethylene removal, both locally and internationally. Furthermore, he also designed airflow-friendly packaging systems for the industry with proven results.

 

Register for free to gain access the digital library for Cold Link Africa publications